by Tami Port MS

Created on: July 02, 2009   Last Updated: July 25, 2009

Germ Theory is the concept that microorganisms can cause disease, and this theory is the foundation of modern medicine. Here is a summary of some key discoveries.

The refutation of spontaneous generation was essential in the development of Germ Theory; the understanding of infectious disease. Spontaneous generation, is the idea that, on a daily basis, living things can arise from non-living matter, a violation of cell theory.

* Aristotle and Spontaneous Generation *

Aristotle was one of the first to record his conclusions on the possible routes to life. He saw beings as arising in one of three ways, from sexual reproduction, asexual reproduction or nonliving matter.

According to Aristotle, it was readily observable that aphids arise from the dew on plants, fleas from putrid matter, and mice from dirty hay; and this belief remained unchallenged for more than two thousand years.

What was actually being observed was the appearance of visible organisms or populations of organisms which arose from microscopic precursors, not spontaneous generation. For example it only takes one bacterial cell to, in a matter of days, give rise to millions of daughter cells, or minute aphid eggs to quickly give rise to visible adult aphids.

* Important Early Microbiologists *

There were many involved in the triumph of Germ Theory, but here is a summary of some of the key players. The first three are covered in this article. To learn more about Pasteur, Lister, Koch, Domagk and Fleming, see the article "Late Germ Theory of Disease".

* van Leeuwenhoek, Anton (1670s)
* Semmelweis, Ignaz (1840s)
* Snow, John (1850s)
* Pasteur, Louis (1860s)
* Lister, Joseph (1860s)
* Koch, Robert (1870s)
* Domagk, Gerhard & Fleming, Alexander (1920s & 1930s)

* Anthony van Leeuwenhoek's Animalcules (1670s) *

During his life, Leeuwenhoek assembled more than 250 microscopes, some of which magnified objects 270 times. Through magnification, he discovered presence of micro organisms; organisms so tiny that they were invisible to the naked eye. He called these tiny living things animalcules, and was the first to describe many microbes and microscopic structures, including bacteria, protozoans and human cells.

* Ignaz Semmelweis and Puerperal Fever (1840s) *

Semmelweis, and Austrian physician, noticed death rates were higher in maternity wards staffed by medical students than in those attended by midwives, and that death rates also went down in summer, when medical students on vacation. Many of these deaths

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